This circuit is for traditional old-style telephone lines found in an American 1980s documentation. Components are common and the optical coupler can be replaced with an equivalent.
This circuit was obtained in an old American manual. The circuit is valid for any operational. The...
This two-relay circuit gives drive logic that is clear when analyzing the circuit. In the original...
This circuit, suggested by Philips Components (1980), uses a fast voltage comparator and requires...